CBT: the thread to centralize your feedback
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@flakpyro that’s exactly the reason we were asking for the cbt option to come available. It’s a huge difference in storage usage and the amount of writes done to the storage. Huge improvement!
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In theory, migrating a VM to another host (but keeping the same shared SR) shouldn't re-trigger a full. It only happens when the VDI is migrated to another SR (the VDI UUID will change and the metadata will be lost).
At least, we can try to reproduce this internally (I couldn't on my prod).
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@olivierlambert Looks like since the last XOA update it no longer triggers a full which is great news. Instead after a migration i see "can't create a stream from a metadata VDI, fall back to a base" when the job next runs. After that it retries and runs as usual.
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Interesting
Where are you seeing this message exactly? -
@olivierlambert
For me it appears in the backup summary on the failed task
And after the job retries. (I have retries set to 3)
I believe others a few posts up are also seeing this same error message. @rtjdamen @manilx
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And only after migrating the VM from a host to another, without changing its SR?
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@olivierlambert Correct. The VM in question is on a NFS 4 SR. The next backup run will run without the error for as long as it stays on that host, however if i move it again the process repeats it self.
We are running paid XOA so if it helps i can enable a support tunnel for you guys to take a look at logs. However we have quite a few nightly backups now so not sure if the logs will have rotated. Either way its in our test environment so we can run the job anytime to generate fresh data.
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That's weird, I'm using RPU in our prod so the VM are moving, but the VDI doesn't change. Anyway, another test to try internally
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@olivierlambert we do not see this error in relation to migration, they just happen at a random situation. I have seen issues with cbt and multidisk vms, could it be that these are multi disk vms?
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@rtjdamen Yes the VM i have been testing with above is a multi disk VM. I will do some testing with a single disk VM and see if that makes a difference.
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@flakpyro this issues we saw were only happening on nfs and multidisk vms. The error was cbt was invalid if i am correct. This is not a xoa error but we saw it on my 3th party backup tool also using cbt
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@rtjdamen After testing with both single disk VMs and multi disk i am seeing it on both. However it is much more common on multi disk VMs.
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@flakpyro are u able to test it on iscsi?
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@rtjdamen I dont not have any iscsi luns mapped to our hosts to test with. We went all in with NFS from iscsi as we moved from ESXi to XCP-NG.
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After the CBT feature was added to the backup method, The error "VDI must be free or attached to exactly one VM" was occurring on our system. Today I upgraded XO to the e15f2a1 and tried taking full and delta backups with Continuous Replication. Now everything works fine.
NBD connection enabled, NBD+CBT backup enabled, XCP-ng 8.2, CR backup from FC storage to NFS storage. -
Great news! Other similar feedback in here?
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@olivierlambert can’t check, running on xoa.
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It will be available in 12 days then
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@olivierlambert indeed haha, most things work like a charm, some issues but i know florent is still working on them.
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Yes, as you can see in here, we are fixing most of the remaining issues to be ready on next week for our next release
